Trip mechanisms

ABSTRACT

A trip mechanism for a stop-watch has a pivotally mounted operating lever movable between two operative positions to inhibit or enable movement of the hands of the watch. An engagement member engageable with the operating lever to switch it between its two positions, is in the form of a unitary plunger having a bifurcated end so as to provide two parts each for engaging a distinct one of two elements, or notches, of the lever in accordance with the position of the lever when the mechanism is operated. A spring is coupled to the lever and acts to bias the lever in the manner of an over-centre toggle into its two operative positions. The plunger extends from its bifurcated end into abutment with the interior of a hollow push-button cap, and is acted upon by a spring to maintain this abutment and at the same time spring bias the push-button into the rest position. Depression of the push-button displaces the plunger longitudinally towards the lever so as to bring about the appropriate engagement of the bifurcated end with the lever notches.

[ July 16, 1974 TRIP MECHANISMS [75] Inventor: Cecil Leslie Boult, near Swansea,

Wales [73] Assignee: Smiths Industries Limited, London,

England [22] Filed: Aug. 10, 1972 [21] Ap pl. No.: 279,400

[30] Foreign Application Priority Data Aug. 20, 1971 Great Britain... 39088/71 [52] U.S.Cl.... 74/100, 58/76 [51] Int.Cl. ..F16h21/44 [58] Field of Search 74/520, 100; 58/229, 76, 58/77, 78, 79; 200/153 J [56] References Cited UNITED STATES PATENTS 448,549 3/1891 Schlatter 58/76 995,681 6/1911 Kanagy' 200/153 .1 1,493,125 5/1924 Pastor 58/76 1,540,247 6/1925 Bowman 74/100 1,658,511 2/1928 Bruynis ZOO/153.9 3,712,036 1/1973 Morita 58/77 Primary Examiner-Benjamin W. Wyche Assistant Examiner--Wesley S. Ratliff, Jr. Attorney, Agent, or FirmGeorge Vande Sande 5 7] 7 ABSTRACT A trip mechanism for a stop-watch has a pivotally mounted operating lever movable between two operative positions to inhibit or enable movement of the hands of the watch. An engagement member engageable with the operating lever to switch it between its two positions, is in the form of a unitary plunger having a bifurcated end so as to provide two parts each for engaging a distinct one of two elements, or notches, of the lever in accordance with the position of the lever when the mechanism is operated. A spring is coupled to the lever and acts to bias the lever in the manner of an over-centre toggle into its two operative, positions. The plunger extends from its bifurcated end into abutment with the interior of a hollow pushbutton cap, and is acted upon by a spring to maintain this abutment and at the same time spring bias the push-button into the rest position. Depression of the push-button displaces the plunger longitudinally towards the lever so as to bring about the appropriate engagement of the bifurcated end with the lever notches.

3 Claims, 4 Drawing Figures PATENTEUJUL'I s m 3.823.612

' sum 2 OF 3 TRIP MECHANISMS This invention relates to trip mechanisms and is more particularly, although not exclusively, concerned with the provision of such mechanisms for controlling the movement of the hands of a stop-watch.

One form of trip mechanism in use at present includes a turret wheel which is rotatable about its axis in a number of predetermined angular steps under the influence of a push rod. The push rod is associated with a push-button and whenever that button is depressed, acts on the turret wheel so as to rotate it. As the turret wheel is rotated it moves one end of an operating lever between two or more, positions. In moving between these positions the lever effects the desired control, for example in a stop-watch the lever may urge a stop-pin end of spring 17 bears against a ledge 18 formed on the inner wall of the sleeve 15, and the lip 14 engages an inner rim-surface 19 of the casing so as to retain the button 13 and the plunger 16. The operating plunger 16 has a bifurcated lower end 21 and terminates in two wedges 22 and 23 engageable with notches 24 and 25 into engagement ,with the balance wheel thereby stopping the watch.

One disadvantage of such a trip mechanism is that means must normally be provided to prevent rotation of the turret wheel in a sense counter to that in which it is to be moved by the push-rod. Again the push-rod acts indirectly on the lever and movement of the lever may therefore be delayed following depression of the push-button.

An object of this invention is to substantially alleviate or overcome some or all of the above disadvantages.

According to this invention a trip mechanism has 'a pivotally-mounted operating-lever which is movable about the axis of its pivotal mounting between first and second positions, and an engagement member which is operable to move towards the lever and engage therewith for switching the lever from one to the other of its first and second positions, the engagement member when operated as aforesaid with the lever in its said first position engaging with a first of two distinct elements of the lever to pivot the lever into its said second position, and when operated as aforesaid with the lever in its said second position engaging with the second of the two elements of the lever to pivot the lever .into its said first position.

A trip mechanism according to the invention and included in a stop-watch will now be described, by way of example only, with reference to the accompanying drawings in which:

FIG. 1 is a rear view of the stop-watch with the casing partially broken away to show part of the trip mechamsm,

FIGS. 2, 3 and 4 are schematic representations of the trip mechanism that serve to illustrate its operation.

Referring to FIG. 1, the casing 10 of the stop-watch houses a movement 11 only part of which is shown. A reset and winding button 12, which may be operated both to wind the watch and to reset its hands to zero, is carried by the movement 11 to extend through a hole in the casing 10. (The reset mechanism may conveniently comprise a mechanism such as is described in my co-pending US. Pat. Application Ser. No. 279,401, filed Aug. 10, 1972). Also passing through a hole in the casing is a stop-start, or brake button 13 for controlling the movement of the hands of the watch.

Referring now also to FIGS. 2 to 4, the button 13 is in the form of a hollow cup having a lip 14 formed at its open end, and is slidably mounted on a hollow sleeve 15 carried by the casing 10. An operating plunger 16 is located within the hollow sleeve 15 and its upper end, which is in the form of a pad, is urged against the inside upper end of the button 13 by a spring 17. The lower respectively formed on a rocker lever 26.

The rocker lever 26 (not shown in FIG. 1) is pivotally mounted at 27 in support plates 28 carried by the casing 10. This lever carries a pin 29 located in the bifurcated end of a brake lever 30 pivotally mounted, at 31, on the movement 11. Levers 26 and 30 are movable under the influence of plunger 16 between first and second positions shown respectively in FIGS. 2 and 4. Attached to the other end of the brake lever 30 is one end of a brake rod 32, the other end of which is fixed to the movement 11 as indicated. A stop pin 34 is carried by the'brake lever 30 and is engageable with the balance wheel of the watch in a known way. Movement of the brake lever 30 about its pivot 31 moves the brake rod 32 and stop pin 34 into and out of engagement with respectively a brake drum 33 mounted on the drive shaft'(not shown) of the hands of the watch and the balance wheel 35.

A stop 36 is formed on the brake lever 30 and is operative, as will be described more fully below, to prevent the hands of the watch being accidentally reset while in motion. A spring 37 which is attached to a pin 38 in one ofthe support plates in the casing 10 and to the pin 29 acts to locate the lever 26 in each of its two operative positions following movement of it, in the manner of an overcentre toggle.

To describe the operation of the trip mechanism it willbe assumed that the watch is initially stopped." That is to say the mechanism is in the position shown in FIGS. 1 and 2 with the brake rod 32 in contact with the brake drum 33, the stop pin 34 engaging the edge of the balance wheel 35, and the plunger 16 retracted into the button 13.

To start the watch the button 13 is depressed against the-action of spring 17 and this acts to move the plunger 16 inwardly toward the lever 26. As shown in FIG. 2, this will'cause the wedge 23 to engage the surface-25 and move the operating end of the plunger 16 sideways. Further depression of the button 13 will push the surface 25 inwardly of the watch and rotate the lever 26 about the pivot 27. During this operation the axis of plunger 16 will be displaced angularly relative to the axis of the stop/start button 13, as shown in'FIG. 3. The spring 37 will, once the lever 26 is past its central position, force the lever 26 to its second operative position (that shown in FIG. 4). With movement of the lever 26 to this position, the pin 29 causes the brake lever 30 to rotate in a clockwise sense about its pivot 31. This inturn moves the brake rod 32 out of engagement with the brake drum 33 and causes the brake pin 34 to release the balance wheel 35. Thus the hands of the watch are free and begin to move. Release of button 13 will allow the plunger 16 to return to its original position, centralising itself as it does so under the influence of spring 17. I

When it is desired to stop the hands of the watch, the button 13 is again depressed and it will be seen that on this occasion the wedge 22 engages the surface 24 and rocks the lever 26 back into the position shown in FIG. 2. Again the spring 37 causes this action to take place with a snap. The pin 29 causes the brake lever 30 to rotate about pivot 31 in a counter-clockwise sense, and the brake pin 34 engages the balance wheel 35 stopping the watch at the same time as the brake rod 32 engages the drum 33. The stop 36 is also moved out of engagement with the lip 39 so that the button 12 may now be depressed to reset the hands of the watch to zero. The purpose of brake rod 32 and brake drum 33 is to lock the spindle carrying the seconds hand so that the effect of backlash in the gear train is eliminated when the hands are reset to zero.

' Alternatively, if so desired, the hands of the watch need not be reset to zero but may be merely restarted, by operation of button 13, and in this way the watch may be used, for example as a match-timer.

I claim:

1. A trip "mechanism comprising an operating-lever having first and second parts rigidly interconnected with oneanother, means mounting the operating-lever on an axis for pivotal movement between first and second positions about said axis, said pivotal axis being located intermediate said first and second parts on said operating-lever, and actuation means which is depressable to effect switching of said lever from one to the other of said first and second positions, said actuation means comprising a unitary plunger member of elongate form, said plunger member having first and second elements thereof spaced from one another transversely of the plunger for engagement with said first and second parts respectively of said lever, means mounting the plunger member for longitudinal displacement from a rest position towards said lever upon each depression of said actuation means to engage said first element of the plunger member with said first part ofthe lever when said lever is in said first position and said second element of the plunger member with said second part of the lever when said lever is in said second position, the said engagement of said first element with Y 4 said first part urging said lever into said second position and of said second element with said second part urging said lever into said first position, and means acting on the plunger member to bias the plunger member resiliently away from said lever into said rest position so as to return the plunger member positively to said rest position following each depression of said actuation means.

2. A trip mechanism comprising an operating-lever having first and second parts spaced from one another,

means mounting the operating-lever on an axis for pivotal movement between first and second positions about said axis, said pivotal axis being located intermediate said first and second parts on said operating-lever, and push-button actuation means that is depressable to effect switching of said lever from one to theother of said first and second positions, said actuation means comprising a hollow push-button cap mounted for selective depression from a rest position, a plunger having a bifurcated end to provide first and second elements spaced from one another for engagement with said first and second parts respectively of said lever, said plunger extending from said bifurcated end into said ,hollow cap to abut with the interior of the cap so that depression of said cap from its restposition depresses the plunger to engage said first element with said first part of the lever when said lever is in said first position and said second element with said second part of the lever when said lever is in said second position, the said engagement of said first element with said first part urging said lever into said second position and of said second element with said second part urging said lever into said first position, and resilient means for biasing the cap into its rest position, said resilient means acting on said plunger to urge it to maintain the said abutment with the interior of the cap.

3. A trip mechanism as claimed in claim 1 including spring means coupled to the said operating-lever to provide an over-centre toggle action by which the operating-lever is biased into one or other of its said first and second positions. 

1. A trip mechanism comprising an operating-lever having first and second parts rigidly interconnected with one another, means mounting the operating-lever on an axis for pivotal movement between first and second positions about said axis, said pivotal axis being located intermediate said first and second parts on said operating-lever, and actuation means which is depressable to effect switching of said lever from one to the other of said first and second positions, said actuation means comprising a unitary plunger member of elongate form, said plunger member having first and second elements thereof spaced from one another transversely of the plunger for engagement with said first and second parts respectively of said lever, means mounting the plunger member for longitudinal displacement from a rest position towards said lever upon each depression of said actuation means to engage said first element of the plunger member with said first part of the lever when said lever is in said first position and said second element of the plunger member with said second part of the lever when said lever is in said second position, the said engagement of said first element with said first part urging said lever into said second position and of said second element with said second part urging said lever into said first position, and means acting on the plunger member to bias the plunger member resiliently away from said lever into said rest position so as to return the plunger member positively to said rest position following each depression of said actuation means.
 2. A trip mechanism comprising an operating-lever having first and second parts spaced from one another, means mounting the operating-lever on an axis for pivotal movement between first and second positions about said axis, said pivotal axis being located intermediate said first and second parts on said operating-lever, and push-button actuation means that is depressable to effect switching of said lever from one to the other of said first and second positions, said actuation means comprising a hollow push-button cap mounted for selective depression from a rest position, a plunger having a bifurcated end to provide first and second elements spaced from one another for engagement with said first and second parts respectively of said lever, said plunger extending from said bifurcated end into said hollow cap to abUt with the interior of the cap so that depression of said cap from its rest position depresses the plunger to engage said first element with said first part of the lever when said lever is in said first position and said second element with said second part of the lever when said lever is in said second position, the said engagement of said first element with said first part urging said lever into said second position and of said second element with said second part urging said lever into said first position, and resilient means for biasing the cap into its rest position, said resilient means acting on said plunger to urge it to maintain the said abutment with the interior of the cap.
 3. A trip mechanism as claimed in claim 1 including spring means coupled to the said operating-lever to provide an over-centre toggle action by which the operating-lever is biased into one or other of its said first and second positions. 